Nerve Cells of Eye's Retina

The retina of your eye consists of many interconnected layers of nerve cells, some of which are sensitive to light. Most people have heard of the two types of photoreceptors used to form images: the rod and cone cells. Recently, a third class of photoreceptors has been discovered in the retina's ganglion nerve layer. These intrinsically photosensitive retinal ganglion cells sense the general brightness of ambient light. They are linked directly to several areas of the brain where they control processes such as regulating pupil size and synchronizing the 24-hour circadian rhythm cycle. In this image the cone cells form the top (green) layer and the ganglion cells are at the bottom.